Deflection yoke assembly



.hllly 4, 1961 F. KRATocHvlL Erm. 2,991,392

DEFLECTION YOKE ASSEMBLY Filed Sept. 24, 1959 y .Pi

United States Patent O 2,991,392` DEFLECTION YOKE ASSEMBLY Friedrich Kratochvl, Hannover-Ricklingen, and' Hans Richter, Hannover, Germany, assignors to Telefunken G.m.b.H., Berlin, Germany Filed Sept. 24, 1959, Ser. No. 842,061 Claims priority, application Germany Oct. Z, 1958 4 Claims. (Cl. 315-27) The present invention relates to detiection means forv cathode ray tubes having ferromagnetic yokes surrounding the electron beam, at least one deflection coil set in the form of a toroid being wound on said yoke.

In electromagnetic deilection means for electron beam tubes, there exists the diiculty that the deection coils carry in addition to the sawtooth deflection current the D.C. anode current of the dellection ampliiier tube. As a result of this, the electron beam is additionally dellected and this additional deflection has to be compensated 'for by special centering magnets.

To avoid this disadvantage, it has been known in vertical deiiection circuits to couple the deflection windings, usually connected in ser-ies or in shunt, to the output tube Via a transformer and to thereby obtain the required impedance match. It has also been known, in the case of a deilection coil directly inserted in the anode circuit of the output deilection tube, to connect a choke parallel to the deflection coil. For this purpose, in cases of horizontal delection, supplemental or buck-ing windings are used to compensate for the effect of the D.C. anode current on the magnet iield.

It is an object of the present invention to use the partial windings of a set of deilection coils as the windings of a transformer, the secondary or secondaries of which are substantially short-circuited.

It is another object of the invention to connect the anode of the ampli-fier tube, for example, of the vertical deflection amplifier with the supply voltage source via one of the partial windings, while the other partial winding is coupled with the irst partial winding via the ferromagnetic core surrounding the beam, and the latter partial Winding is short-circuited. 'I'he ilux lield within the space surrounded by the core remains unchanged if the partial windings have the same total ampere turns.

Still further objects and the entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and speciiic examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modiications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

The drawing schematically shows a circuit arrangement according to the present invention.

I1 denotes the neck of a cathode ray tube which is surrounded by an 'annular core Z of liierromagnetic material. Two deflection windings 3 and 4 of toroidal form are wound on the core 2. The winding 3 is short-circuited, and the winding 4 is inserted between a supply voltage source UB and the anode of a deflection tube 5. A sawtooth wave 6 required for dellection is fed to the control grid of the deiiection'tube 5 in the usual manner. In order not to crowd the drawing, the feedback c011- ice pling circuits conventional in such arrangements for making the deection current linear are omitted. They can be applied -to this circuit without difficulty.

If a current of increasing sawtooth form ows through the winding 4, said current being transmitted to the winding 3 by mutual induction, a magnetic eld 7 is set up between the partial windings 3 and 4 in a conventional manner, said lield being substantially linear in the interior of the tube neck 1. Due to the transformer-type coupling of the partial windings, the D.C. anode current of one partial winding is conlined entirely within the core, so that the flux field of the D.C. current cannot leave the core to cause vfa deflection of the electron beam. As in the conventional circuit arrangement of the deflection coils, it is also possible in this case to obtain matching of the deiiection coils to the deflection amplifier Inube by selection of a suitable turn ratio between the two partial windings 3 and 4. In this case, the primary can be made of high resistance and the secondary, i.e., the short-circuited partial winding -3, can be made of low resistance and can be loaded, for purposes of linearity control, by an adjustable resistance 8, if needed, as shown in the drawing, and also a temperature compensating resistance. In order to obtain a suiiciently linear deection, it is only necessary to provide the two partial windings with the same copper area. In case of several partial windings, it possible to separately short-circuit the individual secondaries.

The invention is not limited to tube circuits. It can be suitably applied to transistor circuits, because in such case, the dellection coils or can be designed with low resistance.

We claim:

1. -In a beam-producing cathode-ray tube, a deflection yoke `assembly comprising, in combination: an annular core surrounding the beam; a set of deection coils wound on said core and including at least two separate partial windings disposed diametrically opposite each other, one of said windings forming a primary winding and another of said windings forming a secondary winding inductively coupled to said primary winding; and means for substantially short-circuiting said secondary winding.

2. In combination with a D.C. supply and with deection ampliiier means having a given anode circuit impedance, a deflection yoke assembly as defined in claim 1 said primary winding being connected to said amplifier means as well as to said D.C. supply, and the total number of turns in said partial being divided therebetween such that the impedance of said primary winding matches said anode circuit impedance of said deflection amplifier means.

3. A deection yoke assembly as defined in claim 1 wherein said short-circuiting means comprise a resistance for controlling the linearity of the tube.

4. A deflection yoke assembly as defined in claim 3 wherein said resistance is temperature-dependent.

References Cited in the file of this patent UNITED STATES PATENTS 2,561,586 Montgomery July 24, 1951 2,606,304 Moore Aug. 5, 1952 2,694,784 Reinhard Nov. 16, 1954 

